Unlike a communication (H2H: Human to Human, H2M: Human to Machine) mainly performed by users using a terminal such as a mobile phone equipped with a lot of user interfaces, there is an intra-machine communication (called Machine to Machine or Machine type Communication, hereinafter described as M2M) as a communication form using a device operable solely without necessity of a direct operation by a user.
In M2M, one or a plurality of devices (MTC devices) are located at ends to collect necessary information as needed, and such devices detect and measure information (sensing data) using a sensing function (e.g., temperatures, seismic intensities and water quantities) that each MTC device has. The detected and measured information is collected at a server (MTC server) configured to manage the MTC devices, and various services are provided to users on the basis of such information. The users receive services via the MTC server on the basis of the information reported from the MTC devices.
As means to establish a communication path between the MTC devices and the MTC server, not only wired networks such as a telephone line, a DSL (Digital Subscriber Line) and an optical communication line but also wireless networks such as mobile phone networks can be used. Especially using a wireless network, since there is substantially no limitation on the installation positions of the MTC devices, the MTC devices can be installed in a wide range, which can be said very effective communication means.
Typical wireless communication systems used for mobile phones or the like, however, are optimized for mobile phones, and such a system is not always optimum for a MTC device that provides a service specific to M2M. For instance, a mobile phone is required to regularly check paging from a network side so as to receive an incoming call for verbal communication addressed to the mobile phone. On the other hand, in the case of a MTC device without a verbal communication function, such a device is not required to be always in a ready state of receiving paging, and therefore such an operation is not necessary. Further, since MTC devices are installed at wide-ranging locations and they are less in contact with users, there is a small possibility for the MTC devices to be placed in a state always receiving electric power. For this reason, the MTC devices have to use limited electric power from battery cells or batteries, and so they are required to minimize power consumption for a longer operation time. Especially electric power consumed by a wireless interface used for communication cannot be ignored, and optimization of a wireless communication system for MTC devices is an issue to be necessarily coped with for the MTC devices using wireless communication. Herein the issue of optimizing a mobile phone network for M2M is currently being discussed in 3GPP (refer to the below-described Non-Patent Document 1 and Non-Patent Document 2).
Further as the installation scale becomes larger, the number of MTC devices operating would be enormous. Therefore when a large number of MTC devices connect to a network simultaneously to start transmission/reception of data, congestion is expected in a wireless network and a core network. Accordingly a system to minimize the concentration of accesses has to be provided.
In this way, considering the reduction of power consumption, it is not practical to always connect MTC devices to a network to secure a connection with a MTC server. Instead, it is appropriate to connect MTC devices to a network as necessary and during a necessary time only. To this end, a possible method considered (Time Control) is to designate a time interval (time zone) for a MTC device to access a network in advance and control the MTC device to access the network during the time interval. When a same time interval is designated for a plurality of MTC devices, there is a need to avoid congestion that might occur when the plurality of MTC devices access a network simultaneously. According to the currently considered method, a MTC device receives, from a network or a MTC server, a notification of a time interval when an access is permitted, and connects to the network at any timing in the designated time. Since access timing is randomly decided by each device, even when a plurality of MTC devices are notified of the same time interval, access timing by each device can be distributed so as to avoid the concentration of accesses. This method can limit access time of a plurality of MTC devices (e.g., a MTC device group belonging to the same group) to a network simply by designating, by a network, a common time interval to the MTC device group. Further since access timing is decided at each MTC device's discretion, management cost on a network side can be reduced.
The following describes the case where a MTC device needs information that another MTC device holds (configuration data, i.e., configuration information). For instance, a MTC device newly connecting to a network (new MTC device) has to acquire information necessary to operate as a MTC device. To this end, the new MTC device firstly accesses a MTC server managing the MTC device and requests necessary configuration information. After the MTC server authenticates the accessing MTC device, the MTC server notifies the new MTC device of necessary information. As a result, the new MTC device starts an operation as a MTC device on the basis of the acquired information.